Armstrong had been facing allegations of using performance-enhancing drugs by the agency and had until midnight Thursday to decide to fight the charges. He notified the USADA late yesterday that he would not. The news led to over 30,000 mentions of the cycling legend and Usada on Twitter since Thursday night, according to data from social analytic service, Topsy. Mentions peaked at more than 5,000 updates between 9 and 10 p.m. ET last night, just as the news was breaking.